1. Field of the Invention
The present invention relates generally to printed circuit boards, and more particularly to connecting components to printed circuit boards.
2. Background of the Related Art
A printed circuit board (PCB) is a structure used in an electronic device to mechanically support and electrically connect a multitude of electronic components. A printed circuit board includes an electrically insulating substrate on which conductive communication pathways known as signal traces are formed. The signal traces are typically etched from conductive (e.g. copper) sheets laminated onto the substrate. A printed circuit board populated with electronic components may be referred to as a printed circuit assembly (PCA) or a printed circuit board assembly (PCBA). The main PCBA in a computer system is the motherboard or system board. Examples of motherboard components include processors, drive controllers, video controllers, primary memory, interrupt controllers, and BIOS, as well as electronic connectors for interfacing with additional components. Electronic components commonly include an arrangement of thin electrical leads, which are connected to the signal traces at corresponding electrical contacts on the printed circuit board.
Several component connection types are used in the computer industry. Three predominant connection types are conventionally known as surface-mount, pin-through-hole, and compliant pin connections. Surface-mount technology (SMT) is a connection type in which the component is mounted directly onto the surface of the printed circuit board, using short pins, flat contacts, a matrix of solder balls such as a ball grid array (BGA), or terminations on the body of the component. A pin-through-hole connection is an older connection type wherein electrical leads on the component are inserted into holes in the printed circuit board from one side of the printed circuit board and soldered to conductive pads on the opposite side of the printed circuit board. Compliant pin or “press-fit” technology eliminates the need for soldering by force-fitting an oversized contact pin into a plated through hole (PTH). The radial pressure between the pin and the plated through hole produces a high-quality electrical connection between the pin and plated through hole.
Historically, a standard thickness for a circuit board has been 0.062 inches (62 mils). This originated during the evolution of circuit boards, when commonly-available 1/16 inch (62 mil) sheets of Bakelite® were used as an insulating substrate for electronic assemblies. (Bakelite is a registered trademark of Momentive Specialty Chemicals GmbH.) The 62 mil thickness remained a standard as circuit boards evolved to include the use of multiple conductive layers and different, more advanced materials. However, increasingly complex systems with more extensive wiring requirements also led to the development of thicker circuit boards containing a greater number of layers. Printed circuit board thicknesses now vary from 62 mils to sometimes more than 200 mils. The use of different printed circuit board thickness has led to a proliferation of different parts and connectors to accommodate the different PCB thicknesses.